On Wed, 18 Jul 2012, Eric Sandeen wrote:

Date: Wed, 18 Jul 2012 14:34:47 -0500
From: Eric Sandeen <redacted>
To: Lukas Czerner <redacted>
Cc: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, tytso@mit.edu,
    achender@linux.vnet.ibm.com
Subject: Re: [PATCH 02/12 v2] Revert "ext4: fix fsx truncate failure"

On 7/13/12 8:19 AM, Lukas Czerner wrote:

quoted

This reverts commit 189e868fa8fdca702eb9db9d8afc46b5cb9144c9.

This commit reintroduces the use of ext4_block_truncate_page() in ext4
truncate operation instead of ext4_discard_partial_page_buffers().

And I think commit 15291164b22a357cb211b618adfef4fa82fc0de3
jbd2: clear BH_Delay & BH_Unwritten in journal_unmap_buffer

fixed the fsx problem referenced in that commit more properly.

You're probably right, I'll test that with your test case and add it
to the description.

Thanks!
-Lukas

quoted

The statement in the commit description that the truncate operation only
zero block unaligned portion of the last page is not exactly right,
since truncate_pagecache_range() also zeroes and invalidate the unaligned
portion of the page. Then there is no need to zero and unmap it once more
and ext4_block_truncate_page() was doing the right job, although we
still need to update the buffer head containing the last block, which is
exactly what ext4_block_truncate_page() is doing.

This was tested on ppc64 machine with block size of 1024 bytes without
any problems.

Signed-off-by: Lukas Czerner <redacted>
---
 fs/ext4/extents.c  |   13 ++-----------
 fs/ext4/indirect.c |   13 ++-----------
 2 files changed, 4 insertions(+), 22 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 91341ec..ceab5f5 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c

@@ -4222,7 +4222,6 @@ void ext4_ext_truncate(struct inode *inode)
 	struct super_block *sb = inode->i_sb;
 	ext4_lblk_t last_block;
 	handle_t *handle;
-	loff_t page_len;
 	int err = 0;
 
 	/*

@@ -4239,16 +4238,8 @@ void ext4_ext_truncate(struct inode *inode)
 	if (IS_ERR(handle))
 		return;
 
-	if (inode->i_size % PAGE_CACHE_SIZE != 0) {
-		page_len = PAGE_CACHE_SIZE -
-			(inode->i_size & (PAGE_CACHE_SIZE - 1));
-
-		err = ext4_discard_partial_page_buffers(handle,
-			mapping, inode->i_size, page_len, 0);
-
-		if (err)
-			goto out_stop;
-	}
+	if (inode->i_size & (sb->s_blocksize - 1))
+		ext4_block_truncate_page(handle, mapping, inode->i_size);
 
 	if (ext4_orphan_add(handle, inode))
 		goto out_stop;

diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 830e1b2..a082b30 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c

@@ -1349,9 +1349,7 @@ void ext4_ind_truncate(struct inode *inode)
 	__le32 nr = 0;
 	int n = 0;
 	ext4_lblk_t last_block, max_block;
-	loff_t page_len;
 	unsigned blocksize = inode->i_sb->s_blocksize;
-	int err;
 
 	handle = start_transaction(inode);
 	if (IS_ERR(handle))

@@ -1362,16 +1360,9 @@ void ext4_ind_truncate(struct inode *inode)
 	max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
 					>> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
 
-	if (inode->i_size % PAGE_CACHE_SIZE != 0) {
-		page_len = PAGE_CACHE_SIZE -
-			(inode->i_size & (PAGE_CACHE_SIZE - 1));
-
-		err = ext4_discard_partial_page_buffers(handle,
-			mapping, inode->i_size, page_len, 0);
-
-		if (err)
+	if (inode->i_size & (blocksize - 1))
+		if (ext4_block_truncate_page(handle, mapping, inode->i_size))
 			goto out_stop;
-	}
 
 	if (last_block != max_block) {
 		n = ext4_block_to_path(inode, last_block, offsets, NULL);